This Project investigates the basic computations at work in making simple social decisions, and contrasts them with simple non-social decisions (e.g., ones based on the value of juice or money, rather than the value of other people). It sets the stage for all the others in investigating how social reward is represented and compares to nonsocial reward. An example of a non-social decision is choosing what to drink by pushing one of several buttons on a soda dispensing machine, an example of a social decision is choosing what person to call to go on a date. Here we address these questions: Are there regions in the amygdala and prefrontal cortex that encode stimulus values at the time of choice, and experienced (hedonic) values at the time of outcome, in the social domain (seeing smiling or beautiful faces), as they do in the nonsocial case (getting juice when thirsty)? Are there neurons specialized for valuation of social stimuli, or do the same cells encode value in social and non-social decisions? Does the valuation of different types of social stimuli require specific sub-circuits? And how are individual differences between people reflected in these processes? We will address these questions by carrying out parallel experiments in humans and rhesus monkeys, using the complementary techniques of fMRI and electrophysiological recording in both species, and using a variety of basic social and non-social stimuli. Comparisons will be made across species and across single-unit, local field potential, and BOLD-fMRI data, as well as with data from the other Projects and across individual differences.